1. Field of the Invention
The present invention relates to a recording head and a recording apparatus in which said recording head is mounted for effecting a recording operation, and more particularly a recording head equipped with a character generator for enabling character recording and a recording apparatus utilizing such recording head.
2. Related Background Art
For recording characters and numerals in a recording apparatus, there is generally employed a character generator composed for example of a ROM for generating character patterns, and the recording of such characters and numerals is achieved by the activation of recording elements of a recording head according to said generated patterns.
On the other hand, ink jet recording apparatuses are becoming popular among various recording apparatuses. Particularly the ink jet recording apparatus of the type in which each recording element is composed of an ink discharge opening, an ink liquid path communicating therewith and an electrothermal converter (hereinafter also called heater element) provided in said ink liquid path, and in which a bubble is generated in the ink by the heat generated by the electrothermal converter and the ink discharge is caused by the state change of ink resulting from expansion or contraction of said bubble, is attracting attention in recent years, because of the possibilities of high-density arrangement of the electrothermal converters and of high-speed recording.
FIG. 5 is a block diagram of a conventional structure for driving the recording head of the above-explained type.
A microprocessor unit (MPU) 31 reads bit map pattern data constituting a character, based on a character code, from a character generator (CG) formed in a ROM 33 connected to the MPU through a bus, and stores said data in an image buffer in a RAM 32. Upon completion of reading and storage of data of a line to be recorded on a recording medium, such as recording paper, the MPU 31 reads, from said RAM 32, the data of a number corresponding to that of the heater elements 40 of the recording head, and stores said data in a register 35. A recording pulse generator 36 generates head driving pulses at timings in consideration of the relative movement of the recording head and the recording medium. AND gates 38 release AND signals of said pulses and the output signals of the register 35, thus selectively driving the heater elements 40 of the recording head through a driver array 39 and effecting the recording operation.
FIG. 6 is a block diagram showing another conventional structure.
The structure shown in FIG. 6 is different from that in FIG. 5 in that the recording head is equipped with a driver array 39, AND gates 38 and a shift register/latch 37 for serial data transfer in addition to the heater elements, whereas the recording head shown in FIG. 5 has the heater elements 40 only.
FIG. 7 is a flow chart showing the recording operation with the structure shown in FIG. 6, which is basically same as that of the structure shown in FIG. 5.
Steps S701-S703 receive data from a host system through an I/F controller 34, and prepare a text buffer in the RAM 32. Then a step S704 reads the code of a character from the text buffer, and subsequent steps S705, S706, S707 calculate the character generator address from said code, read the corresponding CG data and store said data in the image buffer.
Upon completion of storage of the data of a line into the image buffer in steps S708, S709, S710, a step S711 starts a carriage on which the recording head is mounted, and steps S712-S715 effect transfer and recording of data of a column corresponding to the heater elements 40 arranged on the recording head, in synchronization with the movement of the recording head. When the recording of a line is completed in a step S716, a step S717 stops the carriage at a home position, thereby terminating the recording of a line.
As explained in the foregoing, in the structure shown in FIG. 5, the recording head is equipped only with the heater elements, while other components such as driver are provided on a circuit board in the main body of the recording apparatus. Such structure is generally adopted for recording with a low resolving power, for a recording head with a relatively limited number of recording elements, or for reducing the cost of a disposable recording head.
On the other hand, in the structure shown in FIG. 6, the recording head is equipped with the driver, shift register/latch for serial data transfer and AND gates. Such structure, capable of serial data transfer to the recording head, allows to reduce the number of signal lines between the recording head and the main body of apparatus, in comparison with that in case of structure shown in FIG. 5. Moreover, it is capable of easy control of the signal transfer timing, because of the presence of the latch for the output of the shift register. Such structure is effective for reducing the number of lines in case of recording with a high resolving power or a case of recording head with a relatively large number of recording elements.
However the structure shown in FIG. 5, though being suitable for a disposable recording head of relatively simple structure, requires a high-speed MPU if the number of recording elements or the resolving power is increased, because the number of accesses of the MPU 31 to the CG or RAM 32, and the capacity of the RAM 32 has also to be increased according to the increase in the number of recording elements or in the resolving power. Such change will elevate the cost of the MPU or of the entire apparatus, and may eventually lead to a loss in the throughput of recording operation.
Also the number of lines connecting the recording head with the circuit board of the main body including the MPU 31 etc. increases with the increase in the number of recording elements or in the resolving power, thus elevating the cost and causing difficulty in the connecting operation in the mounting of the recording head.
Also if a font is desired other than the standard font stored in the CG of the ROM 33, there is often used an optional font cartridge. Such solution however results in drawbacks of requiring a connector for such font cartridge and a space in the apparatus for such font cartridge.
On the other hand, in the structure shown in FIG. 6, the amount of transferred data or the driving frequency of the recording head has to be increased in case of recording with a high resolving power or using a recording with an increased number of recording elements, and the serial data transfer becomes insufficient in the data transfer rate.